PRINCIPLES OF ENVIRONMENTAL TOXICOLOGY AND CONTAMINATION (PART II)

Table of Contents

1. Index
2. UNIT 5 - Transport and fate of contaminants in the environment
3. UNIT 6 - Principles of toxicokinetics and toxicodynamics
4. UNIT 7 - Biotransformation
5. UNIT 8 - Toxicity Testing
   1. Introduction
   2. Dose-response relationships
   3. Test design and test species
   4. Indicator species
   5. Model organisms
   6. Biomarkers and monitoring studies
6. Glossary of key terms associated with environmental toxicology

Introduction

The main aim of toxicity testing is to predict the toxicity of the chemicals present in the environment in order to improve risk assessment. Standard test procedures can be used for toxicological evaluations involving the use of model species, cell cultured in vitro and in silico approaches. Species selection will depend on the type of toxicity to be investigated, availability, cost, sensitivity and reliability in their response. Both sexes are usually employed although in some case tests may be gender-specific.

Acute toxicity and chronic toxicity are the two main types of toxicity that need to be taken into consideration when assessing the adverse effects of chemicals. Short-term studies may also be performed for subacute or subchronic toxicity. Acute exposure is defined as exposure to a chemical for less than 24 hours. Whereas acute exposure usually refers to a single administration, the other toxicity tests categories are characterized by repeated exposures. Considering vertebrates, subacute exposure usually refers to repeated exposure to a chemical for 1 month or less, subchronic for 1 to 3 months, and chronic for more than 3 months. However, this classification depends on the test species and the particularities and duration of the life-cycle.